Rotatable cam limit switch with variable timing and dwell

Abstract

A rotatable cam limit switch with a switch operating cam mounted directly on a continuously rotating drive shaft and axially shiftable relative to the shaft. The drive shaft is also provided with a "fast thread" for adjustable axial positioning of a timing element in slidable engagement with the cam. Manual axially adjustable yoke elements respectively engage the cam and timing element for establishing preselected switch dwell time and phase relationship between said switch and said shaft.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A rotatable cam limit switch comprising in combination: a housing member;   an electric switch in said housing and including a movable contact member and a cam follower arranged to move said contact member from a first operating position to a second operating position;   a drive shaft rotatably supported in said housing member;   a timing adjust sleeve circumjacent to said shaft and in threading engagement with said shaft for axial adjustment relative to said cam follower and said drive shaft;   an elongated, generally cylindrical, tubular cam having a bore receiving the external surface of said timing adjust sleeve and arranged for axial movement therealong and rotation therewith,   said cam having a raised circumferential surface segment and a depressed circumferential surface segment, each segment extending substantially lengthwise of said cam and partially about the exterior thereof with the peripheral extent of each said segment varying from maximum to minimum between its ends, the surface segments of said cam means engaging said cam follower;   restraining means for preventing relative rotational movement between said timing adjust sleeve and said tubular cam;   dwell adjuster means for moving and maintaining said cam axially relative to said cam follower; and   timing adjuster means for moving and maintaining said timing adjust sleeve axially relative to said cam follower and said drive shaft;   whereby the relative position between said cam and said cam follower on said switch may be selectively determined in accordance with the axial positioning of said cam relative to said drive shaft and the point in a given cycle of rotation of said cam at which said cam follower moves between said raised and depressed surface segments being selectively variable in accordance with the combined rotational adjustment of said cam and said sleeve relative to said drive shaft.   
     
     
       2. The rotatable cam limit switch as set forth in claim 1 wherein said drive shaft includes a threaded portion and said circumjacent timing adjust sleeve includes means for engaging the said threaded portion of said drive shaft to permit axial adjustment of said sleeve relative to said shaft responsive to movement of said timing adjust means. 
     
     
       3. The rotatable cam limit switch as set forth in claim 1 wherein the said threaded timing adjust sleeve includes an annular groove and the said timing adjuster means comprises a threaded yoke positioned on a manually adjustable threaded shaft and having a portion thereof engaging said annular groove for axially and rotatably shifting said sleeve relative to said drive shaft, and wherein said rotatable cam includes an annular groove and said dwell adjuster means comprises a yoke threadingly engaging a threaded shaft and having a portion thereof engaging said groove for axially shifting said cam axially relative to said sleeve and said shaft. 
     
     
       4. The rotatable cam limit switch as set forth in claim 2 wherein the threaded portion of said drive shaft comprises a thread having a linear pitch of approximately 1.80 inches for every 360° measured between centers of adjacent convolutions of said thread. 
     
     
       5. The rotatable cam limit switch as set forth in claim 4 wherein the said drive shaft includes as a portion thereof a threaded surface and said timing adjust sleeve includes an internally extending protrusion received by said threaded surface on said shaft. 
     
     
       6. The rotatable cam limit switch as set forth in claim 1 wherein the said restraining means comprises mating non-circular contoured surfaces externally of said timing adjust sleeve and internally of said tubular cam for preventing relative rotational movement between said sleeve and said cam. 
     
     
       7. The rotatable cam limit switch as set forth in claim 6 wherein said non-circular contour is in the form of a hexagon when viewed in cross section. 
     
     
       8. The rotatable cam limit switch as set forth in claim 1 wherein the cam follower on said switch comprises a laterally extending tubular member having seated in the bore thereof at least one rotatable ball axially slidable in said tubular member and engageable with the external surfaces of said cam at one side thereof and cooperating with switch operating mechanism at the other side thereof. 
     
     
       9. The rotatable cam limit switch as set forth in claim 8 wherein there are positioned two cooperating balls retained in said tubular member, with the uppermost ball engaging the cam surface and the lowermost ball seated intermediate the upper ball and a pressure plate on the actuating means of said switch. 
     
     
       10. A rotatable cam limit switch comprising in combination: a housing member;   an electric switch in said housing and including a movable contact member and a cam follower arranged to move said contact member from a first operating position to a second operating position;   a drive shaft rotatably supported in said housing member, said drive shaft including a threaded portion rotatable therewith;     a timing adjust sleeve circumjacent to said shaft and including thread engaging means for engagement with said threaded portion of said drive shaft, the external surface of said sleeve having a uniform, non-circular cross section along at least a portion of its length;   an elongated, generally cylindrical, tubular cam having a non-circular longitudinal bore receiving the external surface of said timing adjust sleeve and arranged for axial movement therealong and rotation therewith, said cam having a raised circumferential surface segment and a depressed circumferential surface segment, each segment extending substantially lengthwise of said cam and partially about the exterior thereof with the peripheral extent of each said segment varying from maximum to minimum between its ends, the surface segments of said cam means engaging said cam follower;     a threaded timing adjuster shaft rotatably supported in said housing in parallel relationship with said drive shaft;   yoke means carried by and threadingly engaged with said timing adjuster shaft and movable therealong responsive to manual rotation thereof,   said yoke means having an arm portion engageable with said timing adjust sleeve for moving the latter axially along the threaded portion of said drive shaft, thereby to effect relative rotation between said sleeve, said drive shaft and said timing adjuster shaft;   a threaded dwell adjust shaft rotatably supported in said housing in parallel relationship with said drive shaft; and   second yoke means carried by and threadingly engaged with said dwell adjust shaft and movable therealong responsive to manual rotation thereof, said second yoke means having an arm portion engageable with said tubular, generally cylindrical cam means for moving the latter axially along the external surface of said timing adjust sleeve;     whereby the relative position between said cam and said cam follower on said switch may be selectively determined in accordance with the axial positioning of said cam on said timing adjust sleeve and the point in a given cycle of rotation of said cam at which said cam follower moves between said raised and depressed surface segments being selectively variable in accordance with the rotational adjustment of said cam and sleeve relative to said drive shaft.   
     
     
       11. In a rotatable cam limit switch comprising in combination: a housing member;   an electric switch in said housing and including a movable contact member and a cam follower arranged to move said contact member from a first operating position to a second operating position;   a drive shaft rotatably supported in said housing member,   an elongated, generally cylindrical, rotatable cam arranged for axial movement relative to said cam follower, said cam having a raised circumferential surface segment and a depressed circumferential surface segment, each segment extending substantially lengthwise of said cam and partially about the exterior thereof with the peripheral extent of each said segment varying from maximum to minimum between its ends, the surface segments of said cam means engaging said cam follower;     timing adjust means for rotatably shifting said cam axially relative to said drive shaft and said cam follower;   dwell adjust means for moving and maintaining said cam axially relative to said cam follower; and   whereby the relative position between said cam and said cam follower on said switch may be selectively determined in accordance with the axial positioning of said cam relative to said drive shaft and the point in a given cycle of rotation of said cam at which said cam follower moves between said raised and depressed surface segments being selectively variable in accordance with the rotational adjustment of said cam and said sleeve relative to said drive shaft;   the improvement wherein said drive shaft, said timing adjust means and said cam are combined as a unitized assembly including;   a timing adjust sleeve circumjacent to said shaft and in threading engagement with said shaft for axial adjustment relative to said cam follower and said drive shaft; and   said cam having a tubular bore receiving the external surface of said timing adjust sleeve and arranged for axial movement therealong and rotation therewith.